Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $23.69   8.691%   $25.7489   $25.75   $25.75   $25.70  
  Purchase #2 $95.41   6.761%   $101.8607   $101.86   $101.85   $101.90  
  Purchase #3 $112.60   13.367%   $127.6512   $127.65   $127.65   $127.70  
  Purchase #4 $250.91   3.854%   $260.5801   $260.58   $260.60   $260.60  
  Purchase #5 $42.48   12.452%   $47.7696   $47.77   $47.75   $47.80  
  Purchase #6 $246.31   6.817%   $263.101   $263.10   $263.10   $263.10  
  Purchase #7 $210.45   10.818%   $233.2165   $233.22   $233.20   $233.20  
  7 purchase totals = $981.85       $1,059.9280   $1,059.93   $1,059.90   $1,060.00